Do all NICs have MAC Address

SAScooby · 08-04-2004, 05:10 AM

Hi All

Please tell me if all Network Interface Cards have MAC addresses ?

Reason I ask is my Laptop doesnt have a MAC address, anyone want to buy it ?

Laidback · 08-04-2004, 05:21 AM

Quote: Originally Posted by SAScooby

Hi All

Please tell me if all Network Interface Cards have MAC addresses ?

Reason I ask is my Laptop doesnt have a MAC address, anyone want to buy it ?

Yes, if it didn't have one, it wouldn't work.

SAScooby · 08-04-2004, 05:37 AM

thats what I thought, I must then ask is a MAC address of

00 00 00 00 00 00

qualifies as a MAC address

I discovered this yesterday when I plugged my laptop onto a corporate network and could see and browse all over the place without a logon

I then checked my ipconfig /all and found my mac address was all zeros

apparently routers direct traffic by MAC address and without one I was able to go everywhere on the network is this true ? or was the it guy I was talking to smoking his socks ?

Supermike · 08-04-2004, 06:56 AM

00-00-00-00-00-00 is the target MAC address used for ARP brodcasts to determine the MAC>IP mapping of a host. If you want to get to 192.168.1.1 your machine will ARP for it by sending a packet with a Target IP of 192.168.1.1 and a target MAC of 00-00-00-00-00-00, when 192.168.1.1 gets the packet it will respond with it's MAC address and then they can talk directly.

Have you tried a nbtstat -A (your IP) to see what it reports as the MAC on your machine and then try the same command on another machine on the network (with your IP again)? Also are you using DHCP or a static IP? Have you tried browsing the network with another machine - are you prompted to login? - Sorry for all the ?'s, but I have never heard of this before.

SAScooby · 08-04-2004, 07:05 AM

Hi thanks for the questions

nbstat isnt recognized as a command on my pc

I dont need to login to other machines

what I did is take a screen shot of my pcs ipconfig /all

hope it helps, it shows dhcp = yes and my ip address

i have also never heard of no MAC address either (me thinks some hacker will pay lots for this .........)

wait I cant spell

nbtstat works here is the result of the nbtstat

SAScooby · 08-04-2004, 07:19 AM

tried the nbtstat from other machines

MAC address is always 00 00 00 00 00 for my laptop
other machines return a valid MAC addy when i do the same thing with there ip

JC-S60 · 08-04-2004, 07:29 AM

I know I have a MB somewhere with a SIS 900 builtin nic. It has the possibility to assign a MAC address in the BIOS. Still strange it works on a network like this...

I don't think it's worth that much though, MAC addresses can be spoofed...

Joa

Supermike · 08-10-2004, 11:19 PM

Thats strange, but I agree that an all zero MAC is more of a problem, than a benefit to a hacker - there are alot of ways to set a MAC address, just need the right HW. I wonder, have you tried getting outside your LAN with this laptop - like on the internet?

I have read of problems with the SIS boards with built in ethernet having all zero MAC's. Any idea what type of ethernet chipset you have?

SAScooby · 08-11-2004, 01:29 AM

Well it has a SIS900 based network adapter.....so that clears that up, I am using it at the moment through my dsl modem.

I have tried it on one corporate network and all I do is plug in and I am on and able to sniff around with no logon, no password etc, I can browse and even open files on shared drives, apparently because my mac addy is a 00 00 00 00 00 00 all the routers "ignore this" as they were set for mac address based routing, i found this strange and since I am in the telecoms world I showed the sysadm on the site and he was astonished, needless to say they have begun to change a few things

Supermike · 08-13-2004, 04:29 AM

Cool, you may be able to set the MAC from the BIOS if it going to cause a problem. That is really interesting about the browsing shares without a password though - never heard of that. I work at a teclcom as well but I tend to be more focused on the WAN than the LAN in my job. Do you have an idea of the topology (are you connecting to a hub/switch/layer 3 or VLAN switch - before the router)?

Just found this link from Leadtek - check the second question down:

http://www.leadtek.com.tw/support/fa...p?pronameid=57

Note that this is specific to Leadtek, but if youy have an Award BIOS it is probably in the same place (Integrated Periperials > SiS-900 MAC Address input) - not sure what the other garbage is on the Leadtek site - but I would set it to whatever if on the label - if there is one.

Aside from checking the BIOS, you may need to update it - since this problem appears to have been around for a while your mobo's manufacturer probably has a fix.

SAScooby · 08-13-2004, 06:53 AM

Hi thanks for the response

I work as a sub contractor and I tested this on a customers site, so I dont know the topology of the network sorry,

I will check the bios out

Supermike · 08-17-2004, 09:36 PM

Don'y know if you are still having this problem or not, but I asked a buddy who has alot of experience working on computers of all types. He had run into this problem with the SIS chipset before and recalled that he just had to update the drivers and the MAC address either returned or he was able to set it.

Darryl · 08-24-2004, 03:32 AM

Under Windows XP, if you don't have a network cable connected, your MAC address is not available. Might be relevant, might not. Just wanted to chip in.

Have fun,
Darryl.

Chairboy · 08-24-2004, 04:16 AM

BTW, it's NBTSTAT, not NBSTAT.

blurp · 08-25-2004, 12:19 AM

Be very careful where you plug your laptop in with a MAC of all 0's. I'm a systems analyst at a very large GM automotive plant with a flat, switched network. Every so often, someone puts a PLC online without configuring it's MAC (some of the ethernet modules we use come configured with all 0's). It creates such an ARP storm that it takes down large sections of the network (sometimes an entire switch). And at $5000 per minute for downtime (at this plant), you don't want to be the one who causes something like this.

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